Electrical breakdown device



Jan. 8, 1952 c. w. JACOB 8 0 ELECTRIfCAL BREAKDOWN DEVICE Filed Sept. 25, 1944 2 SHEETS-SHEET l III/ III I I III/III gwue/vvfm CARLYLE W. JACOB Jan. 8, 1952 c. w. JACOB 2,582,202

ELECTRICAL BREAKDOWN DEVICE Filed Sept. 25, 1944 2 SHEETS-SHEET 2 FIG. 2

INVENTOR CARLYLE 'W. JACOB BY ATTORNEY Patented Jan. 8, 1952 3 ELECTRICAL BREAKDOWN DEVICE Carlyle W. Jacob, Lynn, Mass., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Application September 25, 1944, Serial No. 555,734

7 Claims. (01. 178-44) of short time duration impulses which upon im-' pingement of remote objects are reflected back (with finite attenuation) to the point of origination. There is thus created a definite time interval between the transmission of a pulse and the reception of its echo which is directlyproportional to the range of the object producing the reflection. This time interval is then applied or recorded on a cathode ray tube to indicate the range of the objects.

There are set forth in the prior art many types of electrical switches which enabletransmission and reception to be carried on from a single antenna. The obvious advantages achieved from this arrangement are namely, conservation of antenna equipment and inherent synchronization between transmitter and receiver antenna orientation. In practice these switches are commonly referred to as duplexers or T. R. boxes 1 and are generally situated in the transmission line network and form in part. the connecting link between the antenna and receiver In general they contain a breakdown gap housed in a non-conducting enclosure filled with a gas such as moist air or the like and is adjusted to ignite upon the transmission of an energy pulse, to thereby decouple the receiver from the antenna. Also provided is an auxiliary electrode known as the keep alive electrode which is held in close proximity to the gap and normally maintained at several hundred volts negative with respect to the gap electrodes. The purpose of this latter electrode is to provide a certain degree of ionization at the gap and thereby assure a rapid breakdown thereof upon the application of a: transmitted pulse, and therefore absolute decoupling of the receiver from the antenna. It has been found, however, that this electrode will often oscillate like a relaxation oscillator and hence fail to produce ions at certain instances as copiously as desired, thereby endangering the receiver.

It is therefore an object of this invention to provide a non-oscillating keep alive electrode for electrical breakdown switches of the class ing an abundant supply of ions in an electrical breakdown switch of the class herein described.

Other objects and features of the present invention will become apparent upon a careful consideration of the following detailed description when taken together with the accompanying drawing, wherein Fig. 1 is a cross-sectional view of a typical embodiment of the present invention taken parallel to the axis of the input and output transmission lines and Fig. 2 is a top. plan view of the embodiment shown in Fig. 1.

Reference is now had to Figs. '1 and 2 in which there is shown a typical embodiment of the present invention, comprising a toroidal shaped resonator having a discharge gap l8 formed by a close approach of the upper and lower surface of the toroid. In other words the resonator is not a complete toroid but has its wall interrupted in the central plane near the axis to provide a discharge gap. Respective input and output transmission lines 10 and -H are-also proto the conducting walls of the toriod at high temperature in accordance with the modern technique of glass to metal seals. The glass vacuum maintaining means comprises an inner cylindrical element l'l, an outer cylindrical element l6 and opposite end portions 26 and also a generally tubular sheath 2| snugly fitted around a keep alive electrode 20 of .01 inch diameter or smaller. 7 This electrode is axially aligned, with the inwardly extending flanges 28 and 29 that constitute the discharge gap Hi. The electrode 20 doesnot penetrate the field of the resonator but is sufiiciently removed from the gap [8 so that when a steady negative voltage -(not shown) is impressed upon it through a suitable fiexiblelead 22 a small degree of ionization will take place in the neighborhood of the gap I8. 7 The voltage impressed upon electrode 20, may be in the vicinity of 1000 volts, applied through a high resistance 21 to prevent excessive power dissipation during the periods of high ionization which occur upon the application of a'transmitted pulse. The operation of the electrode 20 tends to prevent the appearance of relatively high voltages at the inception of the breakdown by permitting the tors. 'rotatable vane: of copper orrbrass in a region of high magnetic field intensity or a retractable plunger protruding into the cavity. Deformation of the'cavity might also 'be employed if the walls are sufliciently thin'and resilient: or even an' adjustment of the clearance of the gap might be employed. For example one-tuning adbreakdown to occur at a somewhat lower voltage. The degree of ionization maintained by the electrode 20 is so small that very little reduction in the amplitude of the received signal results therefrom.

In previous electrical discharge switches electrode 20 contained a substantial portion of its lateral surface-exposed to the gap in order to provide ample ionization and would often oscillate and thereby defeat its fundamental purpose of assisting breakdown. Oscillation has been found to be due to the charging and discharging of the stray capacities associated with the electrode through the high resistance 21 so that the electrode functions as a relaxation oscillator. This defect I have found, may be'remedied by increasing the current density of the keep alive electrode which may be brought about by a variety of means, the most favorable being to encompass all the lateral surface of the electrode 20 such as by use of .the tubular glass sheath 2! thusexposing only'theelectrode tip area and also by reducing the'diameter of the electrode to about .01" or less. I have also discovered that the position of the external resistance' 21 for use in regulating the current of the electrode is also effective in controlling oscilla- 1 tion and that the optimum connection is nearest the electrode and not the source of negative potential.

The apparatus shown in'the drawings may also be providedwith a tuning adjustment such as those commonly used for tuning cavity resona- Such an arrangement might consist of a justment such as the retractable plug I9 may be used. Movement of the plug in and out of the cavity varies the volumeof the resonator '25 thereby affords a tuning provision. A metal housing such as 23 may be provided about the structure in order to protect the glass vacuum maintaining meansfrom shock or mechanical strain.

'It must" be understood that even though I have shown and'described this invention in use with coaxial feed lines and a-toroid'al type electric discharge switch, it may applyto any suitable switch and connecting feed line systems. There fore,'this invention is'not to be restricted except insofar as is necessitated by the prior art and a predetermined degree of ionization in the field of said gap, comprising an auxiliary electrode situated-in close proximity to said gap, a source of steady potential for biasing said auxiliary electrode negative with respect to said gap electrodes, and a non-conducting sheath inclosing all but the tip area of saidauxiliary electrode.

' resonant cavity and a pair of electrodes constitutinga breakdown gap enclosed in a vacuum maintaining means, a means for producing a predetermined degree of ionization in the field of said gap, comprising an auxiliary electrode of 10 mils diameter or less situated in close proximity to said gap, a source of steady potential for biasing said auxiliary electrode negative with respect to said gap electrodes, a non-conducting sheath enclosingall but'the tip area of said auxiliary electrode and a resistance located adjacent said auxiliary electrode and in series with said source of potential for controlling the current through said auxiliary electrode.

4. An electrical breakdown switch having an enclosed breakdown'region, means including a charged conducting a wire extending into said region for maintaining a predetermined degree of ionization therein, and a non-conducting sheath inclosing all lateral surface of said wire, the tip surface area of said wire remaining uninclosed.

5;In combination with an electrical breakdown switch,=-a"keep alive electrode structure comprising a substantially cylindrical conductive wire and a non-conducting sheath inclosing all but the substantially circular tip surface area 'of said cylindrical wire.

'6. Apparatus as in claim' 5 wherein the diameter of said uninclosed substantially circular tip area is of the order of 0.010 inch or less.

7. In an electrical breakdown switch, an auxiliary electrode'wire for facilitating breakdown, a source of voltage connected between said auxiliary electrode and the body of said switch, and means for insulating said auxiliary elec trode from said switch body comprising a nonconducting sheath in contact with and enclosing all of the lateral surfaces of said electrode wire.

CARLYLE W. JACOB.

' REFERENCES CITED The following references are of record in the file of. this patent:

UNITED STATES PATENTS 'Number Name Date 1,986,397 Hund Jan. 1, 1935 2,263,648 Salzberg Nov. 25, 1941 2,404,116 Wolowicz et a1 July 16, 1946 2,413,171 Cliiford et a1 1 Dec. 24, 1946 2,438,873 McCarthy Mar. 30, 1948 2,454,761 Barrow Nov. 30, 1948 

